DISCUSSIONS

 

The experiment is conducted to determine centrifugal pump performance characteristic by for several set of speed centrifugal pump. Efficiency is the benchmark of our experimental and theoretical result.

 

We gain the efficiency by the mathematical representations that were given to us by the lab instructor. Which in turn realize by our data that we gather in the experimental stage namely the torque, the elevation difference (water height), pump suction and delivery pressure.

 

From the result obtain we proceed to the graph section via calculation equation given.

 

For 50% of pump speed

We plot the graph of capacity Q (m³/s) versus the Pump Head (m), the graph show that the head pump gradually decreased with the increased of capacity.

 

Next we plotted the graph for capacity Q (m³/s) versus Break Horse Power (BHP), here the line clearly show that with the increase of capacity the horsepower also increased simultaneously except for the final point, this may due to the condition of the machine.

 

Then with the previous graph obtain we then plotted the graph capacity Q (m³/s)versus efficiency (η dimensionless), here the graph exhibit a concave down nature, with the max point at approximately at 1.2 m³/s capacity which give a max efficiency of 35%.

 

For 75% of pump speed

As we observed the graph of capacity Q (m³/s) versus the Pump Head (m), it show that the head pump decreased with the increased of capacity.

 

Next for the graph of capacity Q (m³/s) versus Break Horse Power (BHP), here the line clearly show that with the increase of capacity Q the horsepower increased proportionally.

 

With both the above graph obtain we now plotted the graph capacity Q (m³/s) versus efficiency (η dimensionless), here the graph follow the same nature as the previous speed but the maximum efficacy had increased to 36% at the capacity of 1.8 m³/s capacity.

 

For 90% of pump speed

Here the graph of capacity Q (m³/s) versus the Pump Head (m), the graph show that the head pump decrease as usual but some reading show that capacity value is not relevant to any mathematical function yet we still follow the procedure of the experiment. We found out that the maximum value of capacity the line is not at the minimum value of the pump head reading,

 

For the graph for capacity Q (m³/s) versus Break Horse Power (BHP), the graph follow the virtue of its previous speed that with the increase of capacity Q the horsepower also increased but the final few points does not comply to this. The final four points which posses the max value occur before the final and maximum value of the capacity.

 

For the last graph where capacity Q (m³/s) versus efficiency (η dimensionless), graph show a similar form as its predecessor but as all the graph that we plot on the 90% pump it is a bit distort but the value of the efficiency is the greatest among the three speeds which is 40%maximum efficiency at 1.7 m³/s capacity. 

 

Our discussion leads us to this assumption as why that the graph is distorted at several speed of pump which is definite the apparatus and the machinery is not in a perfect condition. We can’t really point to any severe parallax error because the reading is gathered from the machine interface directly. This is prove with the lab assistant ask us to not set the pump speed to 100% and the apparatus for gathering the turbine speed is also not in a well operation condition.

 

The only possible errors that could come from any member of the group is slight misreading of the dial but it still in a acceptable value.

 

Understanding of group member is clearly projected on the calculation and graph generation.

 

The outcome of the experiment is to give a first hand experience of what we will be learn in Fluid Mechanic II (KJM492) thus relate it together,

 

 

PERSONAL DISCUSSION

Even though I personally prepare this lab report, I would like to elaborate it for better understanding of both party. I gather this from the lab coordinator, fluid mechanics lecturer and from other suitable source.

 

The maximum volume flow rate through a pump occurs when its net heat is zero H=0, this flow rate is called the pump free delivery achieved when there is no flow restriction at the pump inlet or outlet. In other word there is no load on the pump. At this operating point. volume flow rate is large but H is zero, the pump efficiency is zero because there no useful work. At the other extreme, the shutoff head is the net head that occurs when the volume flow rate is zero achieved when outlet port of the pump is block off. Under these conditions, H is large but volume flow rate is zero. pump efficiency is also zero. Between the two the pump’s net head may increase from its shutoff value somewhat as the flow rate increases, but H must eventually decreased to zero as volume flow rate increases to its delivery value. The pump’s efficiency reaches its maximum value somewhere between he shutoff condition and the free delivery condition. This is called best efficiency point (BEP).

 

 

 

Other error that may occur are from cavitations where there is  a non uniform flow which cause the pressure gradient to shift, this is comment in pump. Also, viscosity also would affect the reading if we would change the fluid in the experiment.