JP2014046910A - Main cooling system of diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a main cooling system of a diesel engine reflected on energy-saving, by controlling a rotating speed of a seawater cooling pump on a flow rate of cooling seawater of a heat exchanger, controlling rotation so as to make the outlet temperature of cooling fresh water become the set temperature by following the temperature, and controlling by adding a variation element such as output of the diesel engine, output of a power generation engine etc., the cooling seawater temperature, piping resistance and efficiency of the heat exchanger.SOLUTION: The cooling fresh water heated by a heating element such as the diesel engine 22 and the power generation engine 23 can be reflected on the energy-saving by controlling by adding the variation element such as the output of the diesel engine, the output of the power generation engine etc., the cooling seawater temperature, the piping resistance and the efficiency of the heat exchanger, by controlling the rotating speed of the seawater cooling pump 27 on the flow rate of the cooling seawater of the heat exchanger so that the cooling fresh water temperature coincides with the set temperature with a cooling fresh water quantity of the cooling fresh water outlet of the heat exchanger 24 as constant.

Description

  The present invention relates to a main cooling system used for a diesel engine.

  Fresh water is used to cool diesel engines used in ships, but the fresh water is generally used for cooling by exchanging heat with seawater.

  As shown in FIG. 1, a schematic diagram of a conventional main cooling system for fuel oil is used to cool a heating element such as a diesel engine 10 and a power generation engine 11, which is composed of a cooling fresh water system and a cooling seawater system, and is heated by the heating element. The cooled fresh water is cooled by heat exchange with cooling seawater in the heat exchanger 9.

  The cooling seawater system takes in seawater from the sea chest 1, passes through the cooling seawater intake pipe 2, operates the cooling seawater pump 4 at a constant amount, and supplies it to the cooling seawater inlet 5 of the heat exchanger 9. Then, the cooled seawater exchanged with the cooled fresh water is returned from the cooling seawater outlet 6 to the sea via the cooling seawater discharge pipe 7 and from the outboard through pipe 8.

  The cooling fresh water system is operated with a constant amount of cooling fresh water from the cooling fresh water pump 12 and connected to the cooling fresh water inlet 14 of the heat exchanger 9 through the cooling fresh water pipe 13, while the cooling fresh water pipe 15 branched from the pipe 13. Is connected to the b port of the three-way temperature control valve 16, and the cooled fresh water supplied to the heat exchanger 9 exchanges heat with the cooled seawater, and then passes through the cooled fresh water pipe 18 from the cooled fresh water outlet 17 of the heat exchanger 9. Cooled fresh water connected to the c port and temperature-adjusted from the a port passes through the cooled fresh water pipe 19, and the cooled fresh water supplied to the diesel engine 10, the power generation engine 11, etc. as a heating element passes through the cooled fresh water pipe 20 and is supplied to the cooled fresh water pump. The circulation circuit returns to 12.

  Referring to FIG. 2 which is a schematic heat balance reference example of the conventional main cooling system, in the cooling fresh water system, the cooling fresh water cools the diesel engine 50, the power generation engine 51, and the like, which are heating elements, and then the cooling fresh water pump 40. (100 m 3 / h), the cooled fresh water exiting the cooling fresh water pump 40 is branched into two directions, one at the cooling fresh water inlet 43 of the heat exchanger 44 and the other at the three-way temperature control valve 42. The cooled fresh water that is connected to the b port and entered from the cooling fresh water inlet 43 of the heat exchanger 44 is heat-exchanged and cooled, and the cooled cooling water is connected from the cooling fresh water outlet 47 to the c port of the three-way temperature control valve 42 and from the b port. This is a circulation circuit that is mixed with the cooling water and supplied to the diesel engine 50 and the power generation engine 51 at a temperature sensor 45 set at a port a at a set temperature 36 ° C.

  The cooling seawater system is a cooling fresh water in which the temperature of the cooling seawater inlet 48 of the heat exchanger 44 and the temperature of the cooling seawater outlet 49 of the heat exchanger 44 are 40 ° C. with the temperature of the cooling seawater taken into account of the temperature of the seawater area. The heat exchange area and the seawater flow rate are determined from the cooling capacity of the system, and the cooling capacity is determined by the capacity of the cooling seawater pump 46 (120 m3 / h), the temperature of the cooling seawater inlet 48 of the heat exchanger 44 and the temperature of the cooling seawater outlet 49. It is determined at a temperature of 40 ° C.

  Although the cooling capacity of the heating element varies greatly depending on the output of the diesel engine 50, the power generation engine 51, and the seawater temperature, in the conventional main cooling system, the set temperature of the a port of the three-way temperature adjustment valve 42 of the fresh water cooling system does not vary. The cooled fresh water from which the temperature is maintained branches in two directions, and the flow rate at the cooling fresh water inlet 43 of the heat exchanger 44 varies depending on the amount flowing to the b port of the three-way temperature control valve 42.

  In the cooling seawater system, the ability of the heat exchanger 44 to exchange heat changes if the discharge amount of the cooling seawater pump 46 is constant and the temperature of the cooling seawater inlet 48 and the temperature of the cooling seawater outlet 49 of the cooling seawater. That the temperature difference between the two is changed, and that there is no change in the cooling seawater capacity, there is no change in the electric energy in the motor of the cooling seawater pump 46.

Patent Publication 2010-269641 Central Fresh Water Cooling System Patent Publication 2010-254281 Marine Engine Cooling Device

Merchant Marine Engine Department Design Manual Piping System Japan Society of Marine Engineers Organization Research Committee December 1978

  As explained in the outline heat balance of the conventional main cooling system, even when there is a change in the output of the heating element such as a diesel engine or a power generation engine and a change in seawater temperature, it is not reflected in the motor power of the cooling seawater pump. is there.

  When there is a change in the output of the heating element such as a diesel engine or a power generation engine or a change in the seawater temperature In the main cooling system, heat exchange between the cooling fresh water and the cooling seawater in the heat exchanger It can also be reflected in the flow rate.

The capacity of the main cooling system takes into account the maximum power output of the heating element, and the seawater temperature is assumed to be the highest temperature expected at the time of navigation. Therefore, if it is reflected in the flow rate of the cooling seawater inlet of the heat exchanger, it can be reflected in the discharge amount of the cooling seawater pump, and the power consumption of the motor can be reduced by changing the rotation speed of the cooling seawater pump.

  In the example of a domestic tonnage 499 type cargo ship, the seawater cooling pump consumes about 10.7% of the power consumed during the voyage. However, in the conventional main cooling system, the cooling seawater pump is operated with a capacity that can cover even 110% of the maximum output of the diesel engine, and the cooling seawater pump capacity depends on the output of the diesel engine, seawater temperature, and pump performance. There is no fluctuation, only the difference between seawater inlet temperature and outlet temperature is generated, and it is not energy saving.

When the flow rate Qf of the cooling seawater pump is 120 m3 / h, the seawater temperature t1 is 30 ° C., and the seawater outlet temperature t2 = 40 ° C., the cooling energy of the cooling seawater H (kj · h) can be calculated by the following equation.
H (kj / h) = Qf * sg * sh * (t2-t1)
Qf: 120m3 / h
sg: 980 kg. m3
sh: 4.18 kj / kg. K
t2: 40 ° C
t1: 30 ° C
H = 120 × 980 × 4.18 × (40-30) = 4916000 kj / h
Kw = H / 3600 = 1365 kW / h.

The main point of this invention is that when the seawater temperature on the coast of Japan is investigated, the monthly average seawater temperatures off the coast of Kagoshima Sata Cape, Wakayama Shionomisaki, Chiba Nojimamisaki, Hokkaido Erimo Cape are as follows: Yes,

Formula H (kj / h) = Qf × sg × sh × (t2−t1)
Therefore, the necessary amount of heat of the cooling seawater pump with the same amount of 4916000 kj / h as the seawater temperature changes is calculated as Qf (m3 · h), and the required amount of cooling seawater is as follows.

In this case, the required amount of cooling seawater is calculated by using the annual average temperature and keeping the cooling energy H (kj · h) of the cooling seawater constant.

  The required power estimate corresponding to the required amount of the flow rate Qf pump of the cooling seawater pump is calculated assuming that the efficiency is constant, and since the efficiency varies depending on each pump, an accurate number is difficult but an approximate number.

The flow rate Qf of the seawater cooling pump is 120 m3 / h, the seawater temperature t1 is 30 ° C., and the seawater outlet temperature t2 = 40 ° C. If the seawater temperature is 30 ° C., 120 m3 / h approximately 13.4 kW / h
At 23 ° C, 80m3 / h Approx. 8.9kW / h
48 m3 / h about 5.4 kW / h at 21 ° C
If it is 10 ℃, 40m3 / h, about 4.5kW / h
As shown in the table above, even if only the change in seawater temperature is seen, it will be a large number throughout the year.

  Also, even on the low-temperature cooling water side, the diesel engine output is not operating at 110% output, and since it changes from 70 to 85% during normal voyage, the calorific value is naturally reduced. The flow rate of the cooling pump will also be affected.

  If the cooling capacity of the cooling fresh water system and the seawater temperature are reflected in the rotation speed of the cooling seawater pump, the heat exchange efficiency naturally deteriorates if the seawater flow rate of the heat exchanger is extremely reduced. Have difficulty.

The key point of this main cooling system is that the cooling fresh water outlet temperature of the heat exchanger can be kept at a set temperature (36 ° C.) and the flow rate of the cooling fresh water pump can be kept constant.
Therefore, a temperature sensor is provided at the cooling fresh water outlet of the heat exchanger, and the discharge amount of the cooling seawater pump may be controlled to reflect the rotational speed of the electric motor so that the temperature of the cooling water passing through the temperature sensor becomes the set temperature. .

  The cooling fresh water heated by a heating element such as a diesel engine or a power generation engine may be controlled so that the cooling fresh water amount at the cooling fresh water outlet of the heat exchanger is constant and the cooling fresh water temperature matches the set temperature. The output of the diesel engine, the output of the power generation engine, etc., and the temperature of the cooling seawater are controlled by controlling the rotation speed of the seawater cooling pump to control the flow rate of the cooling seawater to keep the outlet temperature of the cooling water at the set temperature. The purpose is to reflect energy savings by controlling in consideration of variable factors such as pipe resistance and heat exchanger efficiency.

Means to solve the problem

  In order to achieve the above object, according to the present invention, a heating element such as a diesel engine or a power generation engine is cooled with cooling fresh water, and the cooling fresh water heated by the heating element is cooled by a fresh water cooling pump in a heat exchanger. A cooling fresh water system that is supplied to the inlet, passes through the heat exchanger and is cooled by exchanging heat with the cooling sea water, and is supplied and circulated again from the cooling fresh water outlet to the heating element. In the main cooling system as a cooling seawater system in which the seawater discharged from the cooling seawater outlet is directly discharged out of the ship after being supplied to the cooling seawater inlet of the heat exchanger and cooling the cooled fresh water with the heat exchanger. A temperature sensor is provided in the vicinity of the cooling fresh water outlet of the heat exchanger, the temperature sensor is connected to the controller, and the controller controls the temperature so that the cooling fresh water temperature passing through the temperature sensor matches the set temperature. The discharge amount of 却海 water pump characterized by automatically controlling the rotational speed of the motor of the cooling seawater pump

  The invention according to claim 2 is characterized in that, in the main cooling system according to claim 1, a valve for adjusting the pressure is provided in the discharge side piping of the cooling seawater pump so that the minimum water head can be maintained.

  According to the first aspect of the present invention, the conventional cooling and cooling seawater pump is operated with a constant discharge capacity at the maximum output, but the seawater temperature varies depending on the place on the ship every day during the voyage. In the cooling fresh water system, the main cooling system is to keep the cooling fresh water outlet temperature of the heat exchanger at the set temperature under the condition that the heat generation amount is changed by the output of diesel engine, power generation engine, etc. As the efficiency of the exchanger, seawater temperature, and pump efficiency are aggregated in the cooling seawater volume, monitoring and controlling the cooling freshwater outlet temperature will consolidate the efficiency and efficiently respond to and demonstrate energy conservation. it can.

  The invention according to claim 2 is a case where the seawater is supplied to a high place on a ship because the cooling seawater pump is often used for other purposes in the fuel oil main system according to claim 1. If the seawater flow rate decreases, the piping resistance will also decrease, and the head of the cooling seawater pump will also decrease, which may make it impossible to supply seawater to high places.

  In order to avoid this problem, a valve for adjusting the pressure is provided in the discharge-side piping of the cooling seawater pump, and the minimum head is maintained, so that it can be supplied for other purposes.

Effect of the invention

  In the main cooling system of the present invention, it is possible to control the amount of seawater corresponding to the seawater temperature outside the ship, the cooling freshwater corresponding to the output of a heating element such as a diesel engine and a power generation engine, and the heat exchange efficiency. Reducing the consumption of electric power by corresponding to the discharge amount also contributes to the fuel efficiency of the power generation engine and energy saving.

As an example, a cargo ship having a total tonnage of 499 gross tons has a power output of about 1000 kW at the voyage speed of a diesel engine. Considering the seawater temperature on an annual average, if the power consumption of the cooling seawater pump is 8.9 kW, energy saving is about 0.5%.
Further, the output of the diesel engine during actual voyage is further reduced if the output is about 700%.

FIG. 6 is a schematic system diagram of a main cooling system for a small boat according to a conventional embodiment. It is a reference example of the outline heat balance corresponding to the main cooling system of the small ship which concerns on the conventional embodiment. 1 is a schematic system diagram of a main cooling system for a small boat according to an embodiment of the present invention.

  A schematic system of the main cooling system according to the embodiment of the present invention will be described with reference to FIG. 2. Cooling of the heating elements such as the diesel engine 22 and the power generation engine 23 circulates the cooling fresh water, and the heated cooling fresh water is the heat exchanger 24. In the main cooling system that circulates seawater and cools it by exchanging heat, the cooling seawater system takes in seawater outside the ship from the sea chest 25, passes through the cooling seawater intake pipe 26, and cools the seawater with the cooling seawater pump 27. The seawater supplied to the 24 cooling seawater inlets 28 and heat-exchanged and heated is discharged from the outboard through pipe 31 through the cooling seawater outlet 29 through the cooling seawater discharge pipe 30.

  The cooling fresh water system discharges a certain amount of cooling fresh water by a cooling fresh water pump 32, passes the cooling fresh water pipe 33, supplies it to the cooling fresh water inlet 34 of the heat exchanger 24, passes through the heat exchanger 24, and A cooling fresh water pipe 33 provided with a temperature sensor 36 from a fresh water outlet 35 is a circuit that sequentially returns to the cooling fresh water pump 32 through the cooling fresh water pipe 33 via heating elements such as the diesel engine 22 and the power generation engine 23. Yes.

  The temperature sensor 36 is wired to the controller 37, and the controller 37 controls the discharge amount of the cooling seawater pump 27 by the controller 37 so that the temperature of the cooling fresh water passing through the temperature sensor 36 matches the electric motor 38 of the cooling seawater pump 27. The number of rotations is automatically controlled.

  In the cooling seawater system, when the supply destination of the cooling seawater pump 27 is supplied not only to the heat exchanger 24 but also to cooling water for cooling or the like, when the head pressure is about 0.06 MPa, the cooling seawater pump 27 The discharge pipe 30 is provided with a pressure sensor a and an electric valve b, and is connected to the controller c from the pressure sensor a. When the controller c drops below the set pressure, automatic opening / closing control is performed so that the electric valve b rises to the set pressure. The invention of claim 2.

  In the above system, a cooling fresh water system actually includes a high temperature cooling system, a low temperature cooling system, an air cooling system, and the like, but in this description, they are collectively described as heating elements.

22 Diesel engine 23 Power generation engine 24 Heat exchanger 25 Sea chest 26 Cooling seawater intake pipe 27 Cooling seawater pump 28 Cooling seawater inlet 29 Cooling seawater outlet 30 Cooling seawater discharge pipe 31 Outboard through pipe 32 Cooling fresh water pump 33 Cooling fresh water pipe 34 Cooling Fresh water inlet 35 Cooling fresh water outlet 36 Temperature sensor 37 Controller 38 Electric motor a Pressure sensor b Electric valve c Controller

Claims (2)

  Heating elements such as diesel engines and power generation engines are cooled with cooling fresh water, and the cooling fresh water heated by the heating elements is supplied to a cooling fresh water inlet of a heat exchanger by a fresh water cooling pump and cooled through the heat exchanger. A cooling fresh water system that is cooled by exchanging heat with seawater and is supplied and circulated again to the heating element from the cooling fresh water outlet, and supplies seawater outside the ship to the cooling seawater inlet of the heat exchanger by a cooling seawater pump. In the main cooling system having a cooling seawater system in which the cooling fresh water is cooled by the heat exchanger and then the seawater discharged from the cooling seawater outlet is directly discharged out of the ship, a temperature sensor is provided in the vicinity of the cooling fresh water outlet of the heat exchanger. The temperature sensor and the controller are connected, and the discharge amount of the cooling seawater pump is controlled by the controller so that the set temperature is the same as the cooling fresh water temperature passing through the temperature sensor. Main cooling system, characterized by automatically controlling the rotational speed of the motive.   2. The main cooling system according to claim 1, wherein a valve for adjusting pressure is provided in a pipe on a discharge side of the cooling seawater pump so that a minimum head is maintained.