The Composition Of The Valve Train Of The Diesel Generator Set

The valve train is the control mechanism for the intake and exhaust of the diesel generator. It controls the opening and closing of the intake valve and the exhaust valve according to the working order of each cylinder of the diesel generator to ensure that there is enough gas in the specified time. Fresh air enters the cylinder and exhausts the combusted exhaust gas from the cylinder as thoroughly as possible. At present, the most commonly used four-stroke diesel generator set is the overhead valve type valve train, which is mainly composed of valve components, valve transmission components, intake and exhaust systems and diesel generator booster systems.

1. Valve assembly.

The valve assembly is mainly used to seal the intake port and exhaust port of the diesel generator set, and to ensure the normal ventilation of the diesel generator set. The main components of the valve assembly are valve, valve spring, valve guide, valve seat ring and locking device. The lubrication and cooling conditions of the valve assembly in the entire diesel generator are extremely poor, and it is subject to the impact of alternating loads, high temperature, corrosion, etc. Therefore, these parts are very prone to failure. After the valve assembly is damaged, diesel generators will have many failure phenomena, such as increased fuel consumption, reduced power, difficulty in starting, and abnormal smoke exhaust.

(1) Function.

The valve is divided into an intake valve and an exhaust valve. The function of the valve is to seal the combustion chamber and make the cylinders of the diesel generator get normal ventilation.

(2) Working conditions and materials used.

During the operation of the combustion chamber, the temperature of the intake valve and the exhaust valve is very different. When the diesel generator is working at full load, the temperature of the intake valve is generally around 350°C, and the temperature of the exhaust valve can reach 800°C. The materials used in their manufacture are also different. The intake valve is generally made of chrome alloy steel, and the exhaust valve is generally made of silicon-chromium alloy steel with high temperature resistance and strong corrosion resistance.

(3) Structure.

The valve is mainly composed of two parts: the head and the stem. The valve head has the shape of flat top, convex top and concave top. At present, the flat top is used more, mainly because the shape of the head of the flat top valve is simple, the manufacturing is convenient, and the heating area is small.

In order to increase the intake air volume in the combustion chamber of the diesel generator, the head of the intake valve is generally larger than that of the exhaust valve, because increasing the intake valve can reduce the intake resistance and increase the intake air volume. It is more effective to reduce the exhaust resistance by using the valve. The bevel angle of the valve sealing cone is also different. The intake valve generally adopts a bevel angle of 30°C, and the exhaust valve generally adopts a bevel angle of 45°C. The tapered surface of the intake valve adopts a bevel angle of 30°C, mainly because a smaller tapered surface bevel angle can increase the flow rate of the airflow through the section.

2. Valve guide.

The valve guide provides guidance for the reciprocating valve, and ensures that the valve head accurately falls on the valve seat, and at the same time, it can also transmit part of the heat of the valve. Valve guides are generally made of cast iron, which is prone to wear due to its high temperature and poor lubrication conditions.

Due to long-term mutual friction, the fitting clearance between the valve guide and the valve stem will increase. Under normal circumstances, the gap between the intake valve and the duct is about 0.09mm, and the gap between the exhaust valve and the duct is about 0.12mm. When the clearance increases to the limit value of 0.26mm, the valve guide and valve should be replaced in pairs. If the clearance is too small during assembly, it is easy to cause the valve to be stuck.

3. Valve seat ring.

The valve seat ring is designed for the reciprocating valve, and it is used with the valve to seal the combustion chamber. The valve seat ring is generally made of heat-resistant cast iron and pressed into the cylinder head. Due to the continuous impact of the valve and the corrosion of high temperature and high pressure gas for a long time, the valve seat ring is particularly prone to failure during use. In the long-term work, the conical surface of the valve seat is prone to pitting and pits, and the phenomenon of shortening and widening of the seat ring will also occur.

During the operation of the diesel generator, the failure of the valve seat ring is mainly caused by the continuous impact of the valve, the ablation of the high-temperature gas and the excessive carbon deposits generated by the incomplete combustion of diesel in the combustion chamber.

4. Valve spring.

The function of the valve spring is to ensure that the valve quickly falls on the valve seat ring, closes tightly with the valve seat ring, and prevents the valve from being disconnected from the transmission mechanism due to the inertial force during the opening and closing process. The valve bomb should have enough elastic force. If the elastic force is insufficient or broken, it will directly affect the working condition of the combustion chamber. For this reason, maintenance personnel should check the spring force when assembling the valve spring. When the free length of the old spring is less than the free length of the new spring of the same model by about 4mm, the new spring should be replaced. When the valve contains inner and outer springs, the helical directions of the inner and outer springs should be reversed during the assembly process to prevent a single spring from breaking and ringing another spring.

During the operation of the diesel generator, when the valve spring is broken or the elasticity is insufficient, there will generally be a knocking sound inside the valve cover.

The composition and structure of the top-mounted valve valve mechanism of the diesel generator set is introduced here. If you have any other questions, please feel free to inquire. Jiangsu Starlight Electricity Equipments Co.,Ltd. is one of the earliest manufacturers of generators and diesel generator sets in China. The company relies on high-quality products and good services. It has been widely recognized by users in many fields. At present, it can provide various specifications of diesel generator sets in the power range of 15KW-2500KW. For more details, please contact us with sales@dieselgeneratortech.com.