Monty Roberts wrote:

<snip>

Actually Guys,

I don't see anything abysmal about this design. Since I have designed

these

things before I feel I can give an educated opinion on the subject.

Housing

is a nice scroll, It has a nice radiused cutoff with enough clearance to
prevent debris from causing a problem as well as preventing turbulence

and

cavitation. The blades have radiused leading edges and are curved.
definitely way better than the average sheet metal flat blade version of

the

water pump. not quite airfoil blades, but as close as you can get with

the

material and process limitations. I would say that the Mazda engineers

did

their homework on this one. You might be able to machine a true

stainless

steel airfoil impeller, tailored to the aircraft environment and gain a
couple HP. Unless you are willing to build a pump dyno where you can

control

head pressure and measure flow, power absorbed etc. I don't thing

tinkering

with this pump is a good way to spend your time. Either the designers of
this pump were just being Japanese, or there is some other reason for
needing a pump that is designed this well. I can't see spending the

money

without a reason. Perhaps the flow required is higher or the pressure

drop

across the block is higher than your average piston engine. That is

another

key piece of info you will need to make any meaningful improvements in

the

design. If it makes you feel better, you could use a die grinder to take

of

the casting flash and smooth out the impeller.

Cavitation is a boiling phenomenon. To understand it you have to

understand

how the pump functions. It works by generating a high pressure on one

side

and a low pressure on the other side of the pump. I'm going to use the
somewhat incorrect (especially for centrifugal impellers) analogy of the
airplane wing. It has a high pressure on the bottom and a low pressure

on

the top. If the working fluid is a liquid, imagine you fly fast enough

for

the pressure on the top of the wing to become lower than the boiling

point

of the fluid at ambient temperature. The liquid boils. Small bubbles

form.

This is not the problem. When the local pressure once again rises above

the

boiling point the bubbles implode with great force. So great that they

can

tear away chunks of metal and destroy the pump! THIS is a problem. The
situation I am describing actually limits the speed of hydrofoils. They

go

fast enough and they have cavitation on the foils. Bummer.

Oh,  by the way Paul there is a LOT of room for improvement in impeller
design. Unlike axial designs which are pretty well described by napkin

type

calculations, centrifugal fan/impeller design is still somewhat of a

black

art. The killer is the exit angle determination. Mostly trial and error

or

empirical data. CFD has made this easier, but there are no charts to

look

this up in. Don't believe the equations in the fluids books, they work

for

the final exam or a rough guess, but hardware has a way of embarasing

the

black board designer types.

Monty

I totally agree! 27% efficiency is poor. However I don't think any
shade tree mechanic is going to stumble on a 10% efficiency gain let alone
an impossible order of magnitude claimed by some of these charlatans
selling miracle electric water pumps. Can we say perpetual motion?

Here is a pic of an injected molded impeller out of a  Mazda V6 piston
engine. Unfortunately as you can see it failed.

Paul Lamar

I can't believe that they tried to use a plastic part! This is a terrible
application for plastic. Hot antifreeze with who knows what type of
additives, both factory and aftermarket. Most plastics are very sensitive to
chemical embrittlement from any type of organic solvent. Heat of course
makes it worse! All I can say is......... Bean Counters.

No, a shade tree mechanic will not stumble on meaningful gains. Like I said
you have to use a dyno and a lot of experimentation to get anywhere. Also
there are some significant tradeoffs for gains in efficiency. Your operating
range may decrease. You may get increased chance of cavitation off design
point. To increase the efficiency the cutoff is typically decreased. If you
decrease it too far, you get a lot of noise. In a liquid this can cause
local cavitation and also fatigue the impeller. Another possible mode of
failure for your broken pump. The best approach for us is probably to polish
the impeller, remove any casting flash on the housing. Then optimize the
pump operating point for cruise or climb (which ever turns out to be the
critical case) using different dia pulleys. You can do this using the pump
curves that Bill is generating if you had some power consumption data.

If you will notice at any museum that has modern rocket parts on display,
the only part of the pump  you are allowed to see is the turbine. Which is
usually a 1 or 2 stage reaction turbine. Easily designed using hand calcs.
You will not see the compressors which use radial outflow or mixed flow
impellers on display. A lot of test time and effort goes into designing
these pump impellers and the companies involved are rather sensitive as to
who sees them. Although not a rocket pump, I'm sure that Mazda has put a lot
of time into designing the pump and working out the bugs. Putting the
hardware on an airplane untested is not a really good idea. Try it in a car
first.

As to charlatans and  claims. I have seen products where the manufacturer
actually decreases the efficiency of an electric motor in order to be able
to claim they have a 12 amp product, when 3 would do the job. But the
marketing people want to claim they have the most powerful product on the
market. Typically done with power tools and home appliances. Nothing
surprises me anymore. The ignorance of the general public about technology
permits many abuses.

Monty

3 amps at 12 volts.. 36 watts... .048 HP 80% motor eff. .... .038 HP
is not going to pump very much against any head even in the very very 
VERY unlikely (NEAR impossible) event someone came up with a 100% efficient centrifugal pump. 27% is
more typical and that means only
0.01 mechanical HP is available at the pump shaft to actually pump water. 
Several orders of magnitude less than what is actually required to cool
a high power engine. 

 I don't know why people have so
much trouble understanding this. Electrical .. mechanical never
the twain shall meet.

Paul Lamar
 
The AirCraft Rotary Engine NewsLetter.  Powered by Linux.
ACRE NL web site. http://home.earthlink.net/~rotaryeng/            
Copyright 1998-2002 All world wide rights reserved.

Feet,   0,   5,  10,  15,  20,  25,  30,  35,  40,  45,  50,  55,
PSI, 0.00, 2.25, 4.50, 6.75, 9.00,11.25,13.50,15.75,18.00,20.25,22.50,24.75,
 0,0.000,0.000,0.000,0.000,0.000,0.000,0.000,0.000,0.000,0.000,0.000,0.000,
 1,0.000,0.001,0.002,0.004,0.005,0.006,0.007,0.008,0.010,0.011,0.012,0.013,
 2,0.000,0.002,0.005,0.007,0.010,0.012,0.015,0.017,0.019,0.022,0.024,0.027,
 3,0.000,0.004,0.007,0.011,0.015,0.018,0.022,0.025,0.029,0.033,0.036,0.040,
 4,0.000,0.005,0.010,0.015,0.019,0.024,0.029,0.034,0.039,0.044,0.048,0.053,
 5,0.000,0.006,0.012,0.018,0.024,0.030,0.036,0.042,0.048,0.055,0.061,0.067,
 6,0.000,0.007,0.015,0.022,0.029,0.036,0.044,0.051,0.058,0.065,0.073,0.080,
 7,0.000,0.008,0.017,0.025,0.034,0.042,0.051,0.059,0.068,0.076,0.085,0.093,
 8,0.000,0.010,0.019,0.029,0.039,0.048,0.058,0.068,0.078,0.087,0.097,0.107,
 9,0.000,0.011,0.022,0.033,0.044,0.055,0.065,0.076,0.087,0.098,0.109,0.120,
10,0.000,0.012,0.024,0.036,0.048,0.061,0.073,0.085,0.097,0.109,0.121,0.133,
11,0.000,0.013,0.027,0.040,0.053,0.067,0.080,0.093,0.107,0.120,0.133,0.147,
12,0.000,0.015,0.029,0.044,0.058,0.073,0.087,0.102,0.116,0.131,0.145,0.160,
13,0.000,0.016,0.032,0.047,0.063,0.079,0.095,0.110,0.126,0.142,0.158,0.173,
14,0.000,0.017,0.034,0.051,0.068,0.085,0.102,0.119,0.136,0.153,0.170,0.187,
15,0.000,0.018,0.036,0.055,0.073,0.091,0.109,0.127,0.145,0.164,0.182,0.200,
16,0.000,0.019,0.039,0.058,0.078,0.097,0.116,0.136,0.155,0.175,0.194,0.213,
17,0.000,0.021,0.041,0.062,0.082,0.103,0.124,0.144,0.165,0.185,0.206,0.227,
18,0.000,0.022,0.044,0.065,0.087,0.109,0.131,0.153,0.175,0.196,0.218,0.240,
19,0.000,0.023,0.046,0.069,0.092,0.115,0.138,0.161,0.184,0.207,0.230,0.253,
20,0.000,0.024,0.048,0.073,0.097,0.121,0.145,0.170,0.194,0.218,0.242,0.267,
21,0.000,0.025,0.051,0.076,0.102,0.127,0.153,0.178,0.204,0.229,0.255,0.280,
22,0.000,0.027,0.053,0.080,0.107,0.133,0.160,0.187,0.213,0.240,0.267,0.293,
23,0.000,0.028,0.056,0.084,0.112,0.139,0.167,0.195,0.223,0.251,0.279,0.307,
24,0.000,0.029,0.058,0.087,0.116,0.145,0.175,0.204,0.233,0.262,0.291,0.320,
25,0.000,0.030,0.061,0.091,0.121,0.152,0.182,0.212,0.242,0.273,0.303,0.333,
26,0.000,0.032,0.063,0.095,0.126,0.158,0.189,0.221,0.252,0.284,0.315,0.347,
27,0.000,0.033,0.065,0.098,0.131,0.164,0.196,0.229,0.262,0.295,0.327,0.360,
28,0.000,0.034,0.068,0.102,0.136,0.170,0.204,0.238,0.272,0.305,0.339,0.373,
29,0.000,0.035,0.070,0.105,0.141,0.176,0.211,0.246,0.281,0.316,0.352,0.387,
30,0.000,0.036,0.073,0.109,0.145,0.182,0.218,0.255,0.291,0.327,0.364,0.400,
31,0.000,0.038,0.075,0.113,0.150,0.188,0.225,0.263,0.301,0.338,0.376,0.413,
32,0.000,0.039,0.078,0.116,0.155,0.194,0.233,0.272,0.310,0.349,0.388,0.427,
33,0.000,0.040,0.080,0.120,0.160,0.200,0.240,0.280,0.320,0.360,0.400,0.440,
34,0.000,0.041,0.082,0.124,0.165,0.206,0.247,0.288,0.330,0.371,0.412,0.453,
35,0.000,0.042,0.085,0.127,0.170,0.212,0.255,0.297,0.339,0.382,0.424,0.467,
36,0.000,0.044,0.087,0.131,0.175,0.218,0.262,0.305,0.349,0.393,0.436,0.480,
37,0.000,0.045,0.090,0.135,0.179,0.224,0.269,0.314,0.359,0.404,0.448,0.493,
38,0.000,0.046,0.092,0.138,0.184,0.230,0.276,0.322,0.368,0.415,0.461,0.507,
39,0.000,0.047,0.095,0.142,0.189,0.236,0.284,0.331,0.378,0.425,0.473,0.520,
40,0.000,0.048,0.097,0.145,0.194,0.242,0.291,0.339,0.388,0.436,0.485,0.533,
41,0.000,0.050,0.099,0.149,0.199,0.248,0.298,0.348,0.398,0.447,0.497,0.547,
42,0.000,0.051,0.102,0.153,0.204,0.255,0.305,0.356,0.407,0.458,0.509,0.560,
43,0.000,0.052,0.104,0.156,0.208,0.261,0.313,0.365,0.417,0.469,0.521,0.573,
44,0.000,0.053,0.107,0.160,0.213,0.267,0.320,0.373,0.427,0.480,0.533,0.587,
45,0.000,0.055,0.109,0.164,0.218,0.273,0.327,0.382,0.436,0.491,0.545,0.600,
46,0.000,0.056,0.112,0.167,0.223,0.279,0.335,0.390,0.446,0.502,0.558,0.613,
47,0.000,0.057,0.114,0.171,0.228,0.285,0.342,0.399,0.456,0.513,0.570,0.627,
48,0.000,0.058,0.116,0.175,0.233,0.291,0.349,0.407,0.465,0.524,0.582,0.640,
49,0.000,0.059,0.119,0.178,0.238,0.297,0.356,0.416,0.475,0.535,0.594,0.653,
50,0.000,0.061,0.121,0.182,0.242,0.303,0.364,0.424,0.485,0.545,0.606,0.667,
51,0.000,0.062,0.124,0.185,0.247,0.309,0.371,0.433,0.495,0.556,0.618,0.680,
52,0.000,0.063,0.126,0.189,0.252,0.315,0.378,0.441,0.504,0.567,0.630,0.693,
53,0.000,0.064,0.128,0.193,0.257,0.321,0.385,0.450,0.514,0.578,0.642,0.707,
54,0.000,0.065,0.131,0.196,0.262,0.327,0.393,0.458,0.524,0.589,0.655,0.720,
55,0.000,0.067,0.133,0.200,0.267,0.333,0.400,0.467,0.533,0.600,0.667,0.733,