ENG482 Engines And Turbomachinery 2

ENG482 Engines And Turbomachinery 2

ENG482 Engines And Turbomachinery 2

Question:

Honda GX160T1 Stationary Engine Lab

Introduction

Honda is the world’s largest manufacturer of engines. The GX160 stationary engine is popular because it is reliable, efficient, easy to start and relatively cheap (around A$500 new). It is used to power generators, pumps, welders, and small agricultural equipment such as rotary hoes.

Objective

During this lab, you will disassemble a working engine to investigate many aspects of the engine design. Several measurements are required at particular stages of the disassembly

You will start the engine on 20 – 30ml of fuel so that it does not run for too long and get excessively hot and yet will run out of fuel so that during the disassembly of the carburettor you will not have excess petrol.

Answer:

Introduction

This report is written on the disassembly of GX160 stationary engine, the main objective was to study on its working mechanism, materials used in manufacturing and its working efficiency based on the engine design. Therefore in order for all the theoretical knowledge on the working of this engine to be understood well, it had to be done practical through disassembly of the engine. HONDA GX160T1 used as air compressor, lawn mower, Go-Kart, generators, pumps, agricultural equipment and small construction equipment as commercial, individual and household upon the requirement. The HONDA GX160T1 is selected to perform this lab report due to its wide range of use, easy to disassemble and assemble and compact in size. Therefore this will provide a deeper understanding of widely used 4-stroke, single cylinder, air cooled engine and its operation, (Starodetko, et al 2013).

Dimensions Taken During Disassembly

  1. Bore (B) = 64.2 mm
  2. Stroke (S) = 42 mm

III. Valve timing graph is attested at the end of the report

  1. Valve Diameter (I) Inlet valve stem diameter = 3.2 mm (II) Exhaust valve stem diameter = 3.4 mm
  2. Clearance volume (VC) = 20.10cc
  3. Gasket thickness = 1.2 mm

VII. Length of con rod (r) = 86.2 mm

Calculations Performed

  1. The displacement capacity can be explained as volume swept by a number of pistons located in an engine.

Mathematically representation is:

Vd = π *

(Area of Piston) * Stroke * Number of Cylinders in the engine

Vd = Nc (π/4)B2S    2-8  Vd = 147.5 cc

  1. The total combustion chamber volume includes clearance volume also the volume of gasket

VBDC = Vd + Vc  Vc

(Clearance Volume) = volume of gasket + Combustion volume of cylinder head

Volume of gasket = (π/4)B2*Thickness of gasket

= 4.12 cc

Therefore

Vc = 17cc + 4.12 cc

= 21.12 cc

VBDC = Vd + Vc

= 151.62cc

III. Compression ratio is the ratio of volume of combustion chamber of largest to smallest.

RC = (Vc + Vd) / Vc    2-12

= 151.62/21.12

= 7.18

  1. Ratio of conrod length to the crank offset

R = r/a     2-6  Where

r = Length of control = 88.1 mm

a = Crank offset = Stroke / 2 = 21.5 mm

R = 88.1 mm / 21.5 mm

= 4.09

Discussion: Bore To Stroke Ratio

It is the ratio of bore over stroke; it is 1.53 in our engine. This is termed as an Over square engine. For a square engine the B/S is equal to 1 and for under square engine. The B/S is less than 1. Over square engines have typically less stroke length compared to bore, thereby the movement of the piston from TDC to BDC is less and affecting the friction. In our engine’s case, due to the less stroke length the friction is very low compared with a squared or under square engines, where stroke length is equal or more than the bore length, (Starodetko, et al 2013).

I believe the commercial application of the Honda GX160T1 is more in the market due to adaptability for applications. This might be one of the factors that Honda decided to design this over square engine. The over square engines are good in developing peak torque at high speeds. If we increase in stoke length, this will result on the stroke ratio, typically also leads in increase of overall width of the engine. Due to its wide range of application all over the world, Honda must have considered this aspect and decided the GX160T1 should be over squared.

Maximum And Average Piston Speed

The mean speed of an engine is denoted by Up and the Maximum speed of the engine is denoted by Up.

From the ratio of instantaneous speed over the average piston speed we can find the value of

 

Maximum speed of the engine     = (π/2)*sinθ*[1 + {cosθ/(Sqrt(R2 – sin2θ))}]       2-5

W.Pulkrabek, 2004)

Where, the average piston speed

 

?p = 2SN                                                      2-2 (W.Pulkrabek, 2004)

S = stroke

N= Rpm of engine

Rating 1: 4kW at N = 4000 rpm

?p = 2*0.043m *

= 5.73 m/s

Rating 2: 11N-m at N = 2500 rpm

?p = 2*0.043m *

= 3.6 m/s

Now, to find out the maximum speed of engine we need to find the crank angle (θ), or the ratio of instantaneous speed to average speed of piston. R for the small engines has values of 3 to 4 Since our engine is small and compact we will consider R = 3 and find the instantaneous speed to average speed ratio in order to determine the Maximum speed of engine. The ratio can be found from Figure 2-2 from textbook a page number 41. The ratio seems to be roughly around 1.66 at crank angle of 70 (θ). We are considering the maximum ratio value from the figure 2-2 in order to determine maximum speed of engine, (Amano, 2010).

Up/up= 1.66

Rating 1:

4000 rpm at 4kW

= 1.66

Up = 1.66* ?p

= 9.5m/s at crank angle

θ =70 deg Rating 2:

2500 rpm at 11 N-m

= 1.66

Up = 1.66 * ?p

= 5.98 m/s at crank angle θ =70 deg

Valve stem seal: It helps to distribute the pressure evenly and provide a tight seal for the valve stem. Inlet valve has it.

Reason For Choosing Honda Engine In The Study

According to measurement the value of bore and stroke are respectively 67.4mm and 44.2mm. So it is the over square ratio. Therefore, firstly, this kind ratio can help engine save space. Secondly, it decreases loss of friction during piston working. Thirdly, it has a high compression ratio which is 9.76 (the stand compression is between 8-11). So, it can accelerate mixture gas to combust in combustion chamber. Fourth, with the short stroke, the condor length doesn’t too long so that it can decreases vibration of the piston during movement. Fifth, it has a high speed output, because when the stroke is short, the length from BDC to TDC for piston’s movement will become short, so the times of piston’s reciprocating movements will increase at the unit period time in the cylinder, (Amano, 2010).

In addition, the output power is high (the output speed is proportional to the output power). So there will be a high output speed.

Another ration of bore to stroke for this 4kw engine is that we can use a turbocharger. The ratio of bore to stroke can be changed according to the actual situation on the premise of not changing the displacement volume. For example, this ratio can be changed to square ratio. Meanwhile, we need to install a turbocharger within inlet manifold and outlet manifold, which utilizes exhaust gases to drive a turbine (located in the exhaust manifold) so that turbine can drive the compressor (located in the inlet manifold), to compress air and send to combustion chamber. Thus, the air compression ratio is increased, and the combustion rate is increased, thereby, it will increase the output power. ENG482 Engines And Turbomachinery 2.

Describe the piston and rings, showing your understanding of their function and materials used in their manufacture?

The piston ring is a kind of metal ring, which is embedded inside the piston groove. There are two kinds of rings according its function. They are the compression ring and the oil ring. It is a kind of metal elastic ring with outwardly expanding deformation.

ENG482 Engines And Turbomachinery 2