Large-scale water-cooled starter's preset innovation of weak temperature heating start system

1 Overview

1. 1 background introduction

The problem of low-temperature starting of vehicles in cold regions, especially high-power water-cooled engines, has become an urgent problem to be solved.

At present, different measures have been adopted at home and abroad to influence the low temperature starting factors, such as electric preheating and starting, engine air intake heating, and the use of a starter fluid (a special liquid formulated with ether or other combustion fluids) to inject into the intake pipe to improve fuel efficiency. In the ignition condition, the liquid heater circulation system is a new low-temperature starting assist method newly adopted in recent years. In this method, a coolant pump attached to the liquid heater extracts the coolant from the engine body, and is heated by the liquid heater. Recycled into the engine body, so that the engine body temperature rises evenly to achieve the purpose of starting the engine under low temperature conditions. The low-temperature starting auxiliary method adopted by the high-power water-cooled supercharged diesel engine of a heavy-duty off-road vehicle is a liquid heater circulation system. This article addresses the problem that the engine cannot reach the starting requirements under the low-temperature conditions of the system, through analyzing the existing circulation system. The test results, combined with the principle of the engine cooling system, improved the design of the original system, and proved through experiments that the improved system has achieved the purpose of low temperature starting and is safe and reliable.

1. 2 working principle of liquid heater

The structure of the liquid heater is shown in the figure. The self-contained oil pump of the heater is driven by the motor and sucks fuel. The fuel is sent to the fuel injector through the oil pipe and is injected by the fuel injector through the pressure. The high-pressure oil mist and the combustion-supporting fan are inhaled. The air is mixed in the combustion chamber and ignited by the ignition electrode. After fully burning in the combustion chamber, the gas flows through the heat transfer sheet on the inner wall of the heat exchanger, and most of the heat is transferred to the antifreeze in the heat exchanger sandwich by the heat transfer sheet. In the pipeline, it is forced to circulate by the pipeline pump, enters the engine water jacket through the pipeline, and then exchanges heat with the engine body, so that the engine continues to heat evenly, and a temperature sensor is installed at the inlet of the heater, when the heater water temperature reaches 81, The heater control board automatically cuts off the power supply of the solenoid valve, and the heater turns off. The heater control board blows the cool heater for 150 seconds and then turns off the motor. At this time, the water pump continues to work. When the water temperature is lower than 70, the heater is restarted and the heating is repeated. jobs.

2 design improvements

2. 1 question raised

The low temperature preheating start system used in this vehicle is a closed loop system consisting of a liquid heater, an engine cooling system, and a fuel tank, as shown. Commissioning system, start the liquid heater, about 5 minutes solenoid valve automatically stop the power supply, the engine body, including the cylinder head, the cylinder temperature did not change, just from the interface to the interface section of the pipe temperature rose to 60. In addition to liquid heating The pipe directly connected to the device is also around 60.

2. 2 problem analysis

It can be seen that the internal coolant circulation system composed of the engine water jacket and the oil cooling chamber has a total of five interfaces with the outside world. A thermostat is installed at the interface, and the local maximum temperature of the coolant in the low temperature preheat start system (81) is lower than the temperature (83) at which the thermostat automatically opens, so the thermostat is closed and the water path to the tank is always disconnected while the system is in operation.

It can be judged from the test phenomenon that the heated coolant flowed into the engine and almost passed through the engine's six cylinder liners and the oil cooling water chamber, and most of the coolant flowed directly from the interface back to the liquid heater. This is because the distance between the interface and the interface is very short, and there is a path (this path is the circuit that circulates in the cooling system when the engine is working and the thermostat is not turned on). Because the cylinder water jacket is relatively narrow, there is a certain resistance, and the interface This path between the interface and the interface has very little resistance. Therefore, the coolant often takes this shortcut when it is circulated by the liquid heater pump.

Interface: water tank inlet; interface: hot water return; interface: water tank water return; interface: hot water inlet; interface (: engine water outlet, sealed with screw plug gasket

2. 3 Resolving measures

Based on the above analysis, the system is improved, and the principle of the same, the engine hot water inlet from the interface to the engine interface (, as shown, the outlet remains unchanged. The improved system diagram as shown in Under the action of the heater and water pump pressure, the coolant enters the interface after being heated by the heater (in this case, it is divided into three parts, one part passes through the first and second cylinder water jackets, and the cylinder upper water hole flows into the cylinder head water jacket; The three, four, five, and six cylinder water jackets also flow into the cylinder head water jacket from the cylinder upper water hole; some of them flow into the oil radiator radiator cooling water chamber, and the three parts of the water pipeline meet at the interface and flow to the heater. The resistance of the three parts of the waterway is different, and the flow rate of the coolant is different, which leads to different heat transfer and different temperature rise.

At the inlet of the liquid heater, when the water temperature reaches 81, the heating device automatically shuts off, and the fuel pump stops pumping. At this time, the pump still works. This causes the coolant to pass through the cycle, the heat becomes evener, and the heater inlet coolant temperature Therefore, when the water temperature is lower than 70, the heater solenoid valve will automatically open and the heater will work again. This will follow the design improvement loop of the high-power water-cooled engine low-temperature preheating starting system, and the temperature of the engine body will increase uniformly. .

2. 4 test verification

Installation and adjustment of the improved design, heaters from open to the solenoid valve automatically power off (the temperature sensor at the liquid heater inlet 81 to automatically power off, the pump stops feeding) experienced 12 minutes, then use The temperature meter measures the surface temperature of the engine. The measured temperature is shown as 1, and the temperature of each cylinder in the front and rear engine is improved as shown by 5.

5 Comparison of Engine Temperatures before and after Improvement The test results show that the improved design can make the engine body temperature evenly and continuously increase. The average temperature of the engine body can reach more than 30 minutes in 12 minutes to meet the engine start conditions and customer requirements.

In the actual installation of the system, the following factors affect the heating time and the temperature of the engine block: (1) No thermal insulation layer is added to the pipe, so the heat loss of the system is large; (2) The structure is too compact due to the space limitations of the layout. There are many corners and large flow resistance, and the water flow rate decreases, the heating time is prolonged; (3) Due to the limitations of the engine structure, the hot water inlet (near the second cylinder and not in the center of the engine, which leads to the heating water and cooling water cannot be quickly Mixing causes uneven temperature in various parts of the engine and requires a long time for water circulation.

3 conclusions

This article analyzes and improves the design and installation of the liquid heater circulation system. The improved system enables the engine body to continuously heat up to 30 or more in 12 minutes to meet the technical conditions and customer requirements for starting vehicles in cold regions. Since this method heats the engine body uniformly by heating the cooling water distributed in the engine water jacket and the oil cooling chamber, the engine oil temperature also increases, the engine lubrication conditions are improved, and the conventional preheating mode is overcome because local Caused by the warm-up rough start, pull cylinder, stuck parts and other shortcomings. The improved design of this system has been used on a heavy-duty off-road vehicle. Currently, it is in good working condition and has the advantages of stable combustion, high efficiency, reliable use, and good safety. It has long-term promotion and application significance.